Our studies have emphasized the key role of the liver in regulating plasma CEA levels in both benign and malignant states. The study of liver-CEA pathobiology, metabolism and physiology is key to understanding the clincal use of the CEA assay. Patients who have undergone "curative" surgery for colo-rectal carcinoma, who are being followed with serial CEA levels to select candidates for "second-look" procedures, may have transient elevations of CEA unrelated to recurrent malignancy. One reason for such benign elevations may be viral hepatitis, perhaps secondary to transfusion with CEA positive blood. CEA levels and liver function tests will be obtained on all bloods tranfused into patients entering our ongoing study of the use of serial CEA levels for the selection of patients for second-look surgery after primary resection of colo-rectal carcinoma. We will evaluate the effect of transfusion with CEA positive and negative blood on subsequent CEA levels and liver function tests in such patients. We propose to further elucidate the effect of viral hepatitis on CEA levels both prospectively and retrospectively, by studying patients with known acute and chronic hepatitis and subjects with increased risk of exposure to hepatitis virus, such as contacts of known hepatitis patients. Each hepatitis case will be characterized clinically, and by laboratory data and these findings will be compared to blood CEA levels. Long term follow-up will attempt to relate CEA levels at the time of the initial episode to the subsequent development of chronic liver disease or of cancer.